The present invention relates to stepping motors.
Stepping motors are well known and are usually controlled with the aid of supply circuits which, when actuated, are capable of applying electric currents to the individual windings of the stepping motor, and with the aid of a selection circuit adapted to respond to the control signal by selectively actuating the supply circuits in accordance with a pre-established correspondance to the control signal. For example, in the case of a motor comprising four windings, the control sequence of four consecutive steps may be 1 0 1 0, 1 0 0 1, 0 1 0 1, and 0 1 1 0, the following sequence again being identical to the first, namely: 1 0 1 0. The binary digits are here associated in order with the different motor windings, and the digit 1 indicates, for example, that a winding is brought into the circuit, whereas the digit 0 indicates that the same winding is cut out of the circuit. Motors are known which, because of their construction, are capable of subdividing one revolution into 200 steps, thus repeating the control sequence just described 50 times.
It will be noted that, in the above control sequence, two windings are always connected in circuit at the same time. A control sequence of eight steps can be achieved in which, for some of the steps, a single winding is connected in the circuit. This results in a reduction in the movement of the motor, which is then capable of 400 steps per revolution.
Of great interest because of their precise movement, stepping motors nevertheless suffer from the discontinuous nature of their movement, which is troublesome in certain applications. It results in mechanical noise as well as troublesome vibrations, particularly in hydraulic applications where the stepping motor controls a pump, for example.